Circe chess

Circe chess (or just Circe) is a chess variant in which captured pieces return to their starting positions as soon as they are captured. The game was invented by French composer Pierre Monréal in 1967 and the rules of Circe chess were first detailed by Monréal and Jean-Pierre Boyer in an article in Problème, 1968. It is named for the enchantress Circe, who in the Odyssey instructs Odysseus on how to enter the Underworld and return, just as pieces in Circe chess can return after being killed. Circe is rarely played as a variant game (when it is, it is usually combined with progressive chess), but very often employed in composed fairy chess problems. These are the most usual rules employed in Circe—there are numerous other forms of the game in which the rules of rebirth may vary. For instance, a white pawn captured on b4 is reborn on b2; a black knight captured on f6 is reborn on b8; a black rook captured on the same square is reborn on h8. Castling with a reborn rook is permitted. A reborn pawn regains its initial two-step move option. A captured promoted piece is treated as a piece (not a pawn). If the square that the rebirth should take place on is occupied, either by a friendly or enemy piece, the captured unit is not reborn—it is instead removed from the board and takes no further part in the game (like a capture in orthodox chess).